1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus such as an inkjet recording apparatus, which forms images on a medium by using an image forming body, such as ink.
2. Description of the Related Art
In image forming apparatuses, such as inkjet recording apparatuses, an image is formed on a medium by using liquid ink in which coloring material and additives are mixed into a solvent, such as water, alcohol, or the like. Liquid (ink solvent) remains on the surface of the medium on which the image is formed, and this residual liquid on the surface of the medium can be the cause of image degradation (image defects), rear-side image transfer, cockling, and the like. In the inkjet recording apparatus, it is hence necessary to swiftly remove the liquid remaining on the medium, and various means of achieving this purpose have been devised. In particular, in systems which promote the fixing of the ink by causing the coloring material contained in the ink to become insoluble, or causing the coloring material to aggregate, by making a treatment liquid react with the ink the medium, the amount of liquid deposited on the medium is high, and there is a strong need for the liquid to be removed.
Moreover, if the ink coloring material is fixed principally on the surface of the medium, then depending on the three-dimensional shape (height) of the dots formed on the medium, relief effects may occur in the image formed on the medium. It is possible to eliminate relief effects occurring in the image by leveling (smoothing) the dots constituting the image.
Japanese Patent Application Publication No. 2001-179959 discloses an ink absorbing body and an image forming apparatus and method using the ink absorbing body, in which the ink absorbing body comprises a liquid solvent absorbing body and a separating member that covers at least partially the surface of the liquid solvent absorbing body and allows the ink solvent to pass, while having separating properties with respect to the coloring material of the ink. When ink is deposited on a sheet, the liquid solvent absorbing body is placed in closed proximity to a portion of the sheet through the separating member, and the liquid solvent is absorbed into the liquid solvent absorbing body through the separating member, in such a manner that the coloring material and the liquid solvent of the liquid ink on the sheet are mutually separated. Furthermore, there is also a composition in which a liquid volume sensor which determines the liquid volume inside a high polymer absorbing body is provided, and when the sensor value has reached a prescribed value, then a squeezing mechanism is operated.
Japanese Patent Application Publication No. 9-15981 discloses an excess developer liquid removal apparatus, in which a liquid absorbing body is used to remove excess developer liquid adhering to a drum, after wet development of an electrostatic latent image, and this liquid absorbing body is constituted by a surface layer made of an air permeable material having a surface free energy of 25 mJ/m2 or below, on the outermost layer, and an elastic porous material formed on the layer below this surface layer.
However, when an absorbing medium used for liquid removal, or a pressing medium used for leveling the dots, is placed in contact with the print medium (the ink coloring material on the surface of the print medium) and pressed against same at a prescribed pressure, then some of the ink coloring material may be transferred from the surface of the print medium to the absorbing medium or the pressing medium, thus leading to a marked decline in image quality. Furthermore, if the ink coloring material becomes attached to the absorbing medium or the pressing medium, then it also becomes necessary to carry out maintenance for cleaning or replacing the absorbing medium or the pressing medium, thus giving rise to concerns relating to lower productivity, and reduced durability of the absorbing medium and the pressing medium.
In the ink absorbing body and image forming apparatus and method using same described in Japanese Patent Application Publication No. 2001-179959, although a concrete description is given in relation to the material having separating characteristics which is to be used in the ink absorbing body, no specific quantities are stated for the physical properties of the material, and therefore cases may arise where the ink is liable to adhere to the absorbing body, depending on the type of print medium used. In particular, the liquid is liable to remain between the coloring material and the absorbing body if the liquid is not removed sufficiently from the print medium, due to soiling or deterioration of the absorbing body, or the like, and situations such as this may affect the force of adhesion between the absorbing body and the ink.
Furthermore, in the excess developer liquid removal apparatus described in Japanese Patent Application Publication No. 9-15981, the surface free energy of the liquid absorbing body is specified, but other conditions, such as the surface roughness of the liquid absorbing body, are not specified, and hence there is a probability that the ink coloring material may adhere to the liquid absorbing body, depending on the type of medium used.
Moreover, in the above-described publications, there is no disclosure with regard to the relative magnitudes of the adhesive force acting between the ink coloring material and the medium, and the adhesive force acting between the ink coloring material and the liquid absorbing body. Therefore, depending on the type of medium used, and the surface roughness of the medium, the ink coloring material on the medium may adhere to the liquid absorbing body, and therefore, restriction of the possible range of choice of the media may be expected.